Adenosine acts to modulate a complex array of physiological processes in a wide variety of cell types. Perhaps no other organ demonstrates the diverse cellular action of adenosine better than the kidney. With its numerous types of tubular epithelia, endothelium, vascular smooth muscle, nerves, and hormonal secretory cells, the kidney has become an interesting model in which to develop a unified hypothesis to explain the diverse actions of adenosine as a cellular mediator. Recent technical advances utilizing hybridoma technology has enabled us to target, isolate, and grow renal cells types using monoclonal antibodies directed against cell surface antigens of the targeted cell type, as immunoaffinity reagents. This approach to isolate large numbers of specific renal cells has provided a means to identify which renal cells have adenosine receptors and what post-receptor mechanisms are involved in mediating the action of adensoine. Using these immunodissection techniques, we will isolate and grow primary cultures of cells from two important and functionally distinct segments of the mammalian nephron: the thick ascending limb of the loop of Henle and the collecting tubule, with its various subpopulations of cells. Using these in vitro models of segment-specific cells, it is our intention to determine which cells of the collecting tubule and if cells of the thick ascending limb have adenosine receptors, the site (apical or basolateral) and subclass of those receptors, and the receptor- effector mechanisms (production/inhibition of cyclic AMP, mobilization of cytosolic calcium, coupling to guanine nucleotide binding proteins, and protein phosphoralation) involved following receptor activation.